This invention relates to an engine control system and more particularly to a feedback control system for a multi-cylinder engine.
It has been proposed to employ feedback control systems for engine management. Such control systems sense the condition of the exhaust gases of the engine and adjust the charge forming system so as to maintain the desired fuel/air ratio. Although these systems are quite advantageous, they do not lend themselves to another form of engine management system.
That is, with some engine control systems, it is proposed to disable one or more cylinders of a multi-cylinder engine during some running conditions. The disabled cylinders are permitted to run in an idle like condition and, hence, do not consume any fuel nor require significant power for operation. This gives the effect of having an engine for the powered vehicle that has a variable number of cylinders or the equivalent of variable displacement.
However, where a feedback control system is employed and particularly one which uses an exhaust sensor such as an oxygen sensor, the non-operating cylinders will pump fresh air into the system which will give a false reading of mixture strength. Therefore, when feedback control is employed and one or more cylinders are disabled, then the remaining cylinders may receive an over rich mixture and the benefits of the system are lost or worse.
It is, therefore, a principal object of this invention to provide an improved feedback control system for an engine which also permits certain cylinders to be disabled to improve performance without adversely affecting the feedback control system.